The present invention relates to an aminobenzylamine composition which is liquid at room temperature.
More particularly, the present invention relates to an aminobenzylamine composition which is mainly composed of m-aminobenzylamine and p-aminobenzylamine and is liquid at room temperature, and which is an excellent cold-setting type curing agent useful for thermosetting resin compositions.
Aminobenzylamine is an important compound used as a raw material for heat resistant resins and as a curing agent for epoxy resins. Cold-setting type curing agents are widely used for coating, bonding and casting epoxy resin compositions. Conventional cold-setting type epoxy resin compositions are restricted in use because of their strong smell, undercuring which results from absorption of atmospheric carbon dioxide in the curing process, or inferior heat resistance of the final cured products.
For solving these problems, countermeasures which include the use of larger molecular weight compounds or aromatic amino compounds as the curing agent, have been proposed and practically applied. For example, m-aminobenzylamine is used as a curing agent for epoxy resins. The resulting cured products of these epoxy resins are known to exhibit extremely excellent heat resisting properties and adhesive properties (N R L Report No. 6,439; U.S. Pat. No. 3,317,468; and U.S. Pat. No. 3,794,540).
The compound, m-aminobenzylamine, has a melting point of about 40.degree. C. and is solid at room temperature. When the compound is applied as the curing agent for epoxy resin with a purpose as described above, the compound is poorly miscible with other components in the epoxy resin composition and as a result is insufficiently mixed with those components. As a result, the reaction with epoxy resin does not proceed uniformly and quickly. The cured product does not exhibit good adhesion of bonding, adhesion of coating, or physical strength.
For over coming these drawbacks, organic solvents have been used, but safety problems occur from evaporation of the solvents in the curing stage. Also, bubbles formed in the resin by the evaporating organic solvents reduce the bonding power, adhesion of coating, and physical strength of the cured product.
A method of employing modified m-aminobenzylamine for a liquid adduct has also been tested and satisfactory results have not yet been obtained because of, for example, reduction in the adhesive property.